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CharlesMouse

Coleco ADAM RAM Expansion options - Advice please

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Posted (edited)

Is there a technical manual available for the Adam?

Yes there is, I can't place the link at the mo' but I'll post it when I remember.

 

 

Grrr, I think I'm getting silly now:

-A15 line, doh! Reinstated (That will be another patch wire for my current board - I wonder if that will fix the funny RAM report in File Manager 3.0?)

-B0-B2 whacked on to A16-A18...

...what about B3?

 

-Bah! Lets add another 4mb RAM IC (nuts)

-B2 swapped for B3 on the second IC...

...I think I'm getting a bit dirty now. I guess that will work but I've applied no brain cells to the iteration - thoughts?

 

So... having proven to everyone that at best I don't properly sanity check my designs properly and at worst I am clueless what do you say to an 8mb RAM board for the ADAM?

(assuming I haven't done anything else truly stupid)

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Edited by CharlesMouse

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Posted (edited)

That would have both chips responding to all addresses, except that when B2 or B3 is active they will respond differently. Unfortunately, the extra logic needs to be on the chip select lines, with both chips using B0-B2 in the same address scheme.

 

The CAS lines need an OR gate for each line. CS on one chip will be CAS | B3, while CS on the other will be CAS | NOT B3. On the good side, you do have a few NOT gates left to play with. On the bad side, though, you need to add an OR gate.

Edited by ChildOfCv

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Posted (edited)

Thank you you once again. A, hopefully, better attempt shortly

 

A general question:

This new 'design' is the result of boredom and a sleepless night making me wonder if I could make a smaller board with fewer IC's. Then having B3 dangling urged me to add another RAM chip...

-1mb already silly?

-If the cost of a smaller board is more RAM that's fine

-8mb is stupendously pointless

-Now you've gotten this far just do it and nuts to the pointlessness.

 

...if only Hex NOR gate ICs were a thing. Not quite enough logic to use a 7402 in place of the 7404.

Edited by CharlesMouse

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Posted (edited)

I would be interested in 16MB, 32MB, 256MB or larger memory expander for the ADAM computer. A talented programmer could use the extra memory instead of using it as a copy buffer. A new version of File Manager could be created so a 256MB copy buffer could be used.

 

I have been told that File Manager (and maybe some other programs) does work with 2MB memory expanders. Right now I only have a 1MB memory expander, but if I had at least a 2MB memory expander then that would be ideal for me to copy my 1.44MB disk images and use the 2MB memory expander as a copy buffer. Those that own hard drives for the ADAM comptuer could use a 256MB memory expnader as one big copy buffer.

 

If you start making home brew memory expanders at 2MB and above my interest in this project well greatly increase since I may want to solder my own 2MB to 256MB memory expander to use in my ADAM computers.

Edited by HDTV1080P

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Posted (edited)

@HDTV1080P:

I sincerely hope I'm homing in on a working 8mb design and if so and you find it useful I'll be most pleased indeed.

 

I also hope I haven't made any further stupid mistakes, I really have made a meal of this one. Many thanks to everyone, especially ChildOfCv for your most helpful pointers and patience.

 

Fingers thoroughly crossed!

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Edited by CharlesMouse

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Posted (edited)

If you do get a printed circuit board printed up and solder 8MB of memory on it. Let me know what File Manager sees. Awhile ago when I was playing around with a memory expander with 64MB installed, I thought File Manager mentioned 16MB of memory.

 

See this post where I tried to install 64MB of memory on a existing 1MB memory expander and it would not fit in the ADAM computer. Your doing the correct time consuming method of designing the circuit board from scratch.

 

http://atariage.com/forums/topic/269242-colecovisionadam-misc-scans-third-party-controllers-and-other-stufff/?p=4182084

Edited by HDTV1080P

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Posted (edited)

The ideal thing to do for the ADAM memory expander is to modify a solid state drive so that it works in the ADAM as a memory expander out of slot number 3.

 

Or make a ADAM memory expander that has a full size SDXC card slot so one could plug in a 64GB SDXC card into the memory expander. Then when the power goes off the 64GB SDXC card would still maintain its memory.

Of course that would be a lot more work in both hardware and software programming.

Edited by HDTV1080P

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Posted (edited)

It's funny. Now that I think about it your adventures with memory is a large part of what got me to jump down this rabbit hole.

 

Yes, I could see the merits of a SDXC- based solution but at least for now that's going to be biting off more than I can chew. An old-school option would be battery-backed RAM.

 

Now I've got what little brain I have in gear (with much help!) I think I'm closer with this board. I was more than chuffed with the 1mb version but wanted to see if I could do something neater and the extra RAM sort-of arrived for free.

Edited by CharlesMouse

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Posted (edited)

I would be interested in a battery on the memory expander so that it holds its memory when the power is turned off. However a jumper would need to be a option for those people that want to bypass the battery and prefer the memory expander to lose its memory when the ADAM computer is turned off.

Edited by HDTV1080P

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Posted (edited)

I would be interested in a battery on the memory expander so that it holds its memory when the power is turned off. However a jumper would need to be a option for those people that want to bypass the battery and prefer the memory expander to lose its memory when the ADAM computer is turned off.

 

Done, and done. :-)

 

Battery backup could be a very nice thing to have, a non-volatile RAM disk being something I'd quite like - of course I've no idea if there's any software available that could cope with such a thing. It's probably obvious I can barely make a PCB, coding is quite beyond me.

Can you spot the spelling mistake(s)..? I really must get some sleep.

 

 

...I just hope the general consensus is the pesky thing will work and I'll go make another order with Seeed.

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Edited by CharlesMouse

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Just wondering, what is Seeeeeeeeed's turnaround time? I've ordered a few times from Osh Park and typically it's a couple of weeks before it arrives. Would be nice to find a faster source.

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Just wondering, what is Seeeeeeeeed's turnaround time? I've ordered a few times from Osh Park and typically it's a couple of weeks before it arrives. Would be nice to find a faster source.

 

It's about the same, sometimes a bit quicker, sometimes slower... it seems to be mostly about the postage with them - when I put in an order their updates suggest the PCB fabrication is done in about 2-5 days. They do have options for fast delivery but I'm too cheap to have tried that.

 

 

Forgive my paranoia, I'm about to send this design off to Seeeeeeeeed (:-)) but I've made so many mistakes with this project confidence is low. Do you think the latest design looks reasonably sound?

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The logic looks good.

 

I was going to comment about using pull-up resistors on CLK and IORQ, but then I remembered the scheme again. With KD enabled, CLK is driven by the 4048 and IORQ is used to drive the circuit. With KD disabled, IORQ has no effect because the 4048 is in high impedance mode, and therefore CLK can be hooked up directly with no problems. So it turns out that we're good there.

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The logic looks good.

 

I was going to comment about using pull-up resistors on CLK and IORQ, but then I remembered the scheme again. With KD enabled, CLK is driven by the 4048 and IORQ is used to drive the circuit. With KD disabled, IORQ has no effect because the 4048 is in high impedance mode, and therefore CLK can be hooked up directly with no problems. So it turns out that we're good there.

 

Awesome. :-)

 

Right, gerbers off to Seeed. I really appreciate your invaluable advice on this project, I doubt I would have gotten this far without it. Thank you again.

 

Fingers crossed...

 

PS

Time to see if that AY board of mine actually works before the final parts arrive for the 80 column card arrive & I find out how far from functional that is - will the horror show never end..? :-D

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Good news!

 

I have a working 8Mb RAM board in my ADAM. :-D

 

My sincere thanks for all the encouragement and most helpful advice,

 

To recap:

-A new 8Mb RAM board for the ADAM

-Does not need a middle slot card for full function but can make use of one

-Battery backup is an option

 

A few piccies and a repost of the Gerbers for anyone who wants to make their own included below. As can be seen I've yet to add the batter holder - STILL waiting on parts! I've included a photo of my IDE board and the simple mod I made for easy access to the /IORQ line.

 

PS

So that's the Coleco Game Pad and memory board projects sorted, now I need to get that darn 80 column card (and it's add-ons) running and pluck up the courage to dissemble my ADAM to try my latest take on an internal AY card and I'll be happy.

 

PPS

I've got a terrible memory, for those I've been in touch with via pm please send me a reminder.

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ADAM_Mem_8mb_v2_BAT_77.5x56.zip

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I've been meaning to install an F18A and this seems like a great idea to add at the same time, is there a shop link I missed somewhere?

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Hi,

I'm glad you like the look of this project, I hoped it would prove useful to some. On the subject of "where to buy" I'm afraid the interest for me is in the design process and learning about the system I'm currently attacking, I don't generally sell completed versions or kits.

Having said that I really don't mind if anyone else wants to and while I have spare PCB's I'm happy to discuss sending one to anyone who can make use of it. Feel free to PM me.

 

To the thread in general my "master plan", such as it is, is not only to provide useful designs for others where I'm able, but also to help get others in to soldering up their on kit possibly as a starting point to make their own stuff from scratch.

-It is fun, honest!

-Soldering is dead easy with a little practice

-PCB design has a fairly steep learning curve initially but gets easier

-PCB manufacture couldn't be simpler

-As time goes by goodies for somewhat unloved machines like the ADAM will only come from enthusiasts.

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I put my board layouts on Osh Park as an easy way for anyone to order, with the caveat that they make you order at least three, so it is not the most cost effective, but better than nothing. It also means I don't have to provide support if I were to sell the boards and folks did crazy things (like I usually do) and put one of the chips on backwards.

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